Fat and Breeding Cycles in a Montane Population of Sceloporus graciosus

Sceloporus graciosus, at 1600m on the western slope of the California Sierra Nevada, is active from mid-April (males) or early May (females) until late August (females) or late September (males). Young and immature lizards are active from mid-April to early October. Fat accumulates at the end of the breeding season to maximal levels prior to hibernation. During dormancy, males use about half the autumnal fat, at a rate of 0.04 KCal/gm body weight/month. During dormancy, females use 0.01 KCal/gm body weight/ month. In the spring in females fat is used for egg production, and fat bodies shrink as eggs develop. Liver lipids of females are maximal during ovogenesis. Breeding females comprise two size groups: about 2/3 females are estimated 2-3 years old (49-58 mm SLV) and 1/3 are estimated 4 or more years old 59-4 mm SVL). The smaller group has a mean clutch size of 4.80 ane d the larger has a mean clutch size of 5.41 ? .23. Most of the larger females breed at the ae ea beginning of the breeding season (in late May) and younger females may breed from the same time until July. A few large females may lay a second clutch, but a single clutch is the rule. Incubation takes at least 6 or 7 weeks but a late summer decline in soil temperatures seems to prolong development. It is suggested that, under certain conditions, a few young may not emerge until spring.